1. Field of the Invention
The present invention relates generally to a responding apparatus, or copier, more specifically, to a paper handling system for said copier for loading and unloading a sheet of recording paper from a paper stack to and from a printing drum.
2. Description of the Prior Art
For a drum type copier, automatic paper handling requires that paper be fed automatically from a paper stack to a drum, be loaded thereonto and be unloaded or removed therefrom. A common technique used for automatic paper handling involves the utilization of friction associated with a rubber roller or a rubber belt. Disadvantages of the technique include paper jam, double feeding, oblique feeding and other feeding problems resulting from differences in paper weight, surface conditions, etc. Therefore, this technique is not suitable for different types of paper. Another technique used for automatic paper handling (or feeding) involves the use of a vacuum, such as that which is shown in laid open Japanese patent application No. 101719/76. Said another technique utilizes a paper feeding apparatus including a rotary cam and a sucking means driven by the cam via an arm, for sucking the top sheet from a stack of paper and supplying the sheet to a set of transfer rollers. This apparatus often experiences a problem involving the feeding of more than one sheet. In addition, since said sheet is transferred to the next stage via transfer rollers, the above-mentioned disadvantages associated with the former technique may also be caused to occur with respect said another technique.
Other automatic paper loading techniques are also disclosed, for example, techniques disclosed in laid open Japanese utility model application Nos. 75345/74 and 56826/78. In the former technique, a holding means is provided on a drum surface along a longitudinal axis thereof for holding a leading edge of a paper sheet. The holding means opens, when driven by a cam, at a specified rotational position of the drum in order to accept the leading edge of the sheet. The paper sheet held by the holding means is wrapped around the drum due to the rotation of the drum. It is, however, difficult to provide a high quality recorded image on said paper sheet because the sheet is not tightly mounted on the drum surface. In the latter technique, a second holding means is provided to hold the trailing edge of the sheet. However, a new problem is created related to limitation of paper size useable for said copier.